As a dust-collecting filter typified by a diesel particulate filter (DPF), there is used a filter that is made of ceramics having a honeycomb structure. Such a filter has a structure in which at end faces of a honeycomb structure including a number of cells acting as through channels of fluid, the cells being partitioned and formed by a porous partition wall, adjacent cells are plugged at one end on sides opposite to each other so as to exhibit a checker wise pattern.
When an exhaust gas containing fine grains such as particulates is made to flow in from one end face of this filter (plugged honeycomb structure), this exhaust gas flows in an internal part of the structure from one cell which end on the side of this one end face is not plugged and penetrates the porous partition wall, and enters the other cell which end on the other end face side of the structure is not plugged. Further, fine grains in an exhaust gas are caught at the partition wall on the occasion of penetrating this partition wall, and the purified gas which fine grains have been removed is exhausted from the other end face of the honeycomb structure.
Normally, to manufacture a plugged honeycomb structure of such structure, as is illustrated in FIG. 2, adopted is a method in which a masking film 11 acting as a mask is attached to an end face of a honeycomb base material 10, a slurry supply hole 11a is formed in a position corresponding to an open end of a predetermined cell 12 of this masking film 11, an end of the honeycomb base material 10 is immersed in a container in which a plugging slurry 20 is stored, and thereby the plugging slurry 20 is made to enter the open end of the predetermined cell 12 through the slurry supply hole 11a of the masking film 11 (for example, refer to Patent Document 1).
There is disclosed a method in which a slurry having thixotropic properties is used as the above-mentioned plugging slurry, and this plugging slurry is made to enter the predetermined cell of the honeycomb base material while it is vibrated (for example, refer to Patent Documents 2 and 3).
[Patent Document 1] Japanese Patent Application (Laid-Open) No. 2001-300922
[Patent Document 2] Japanese Patent Application (Laid-Open) No. 1994-190218
[Patent Document 3] Japanese Patent Application (Laid-Open) No. 1994-190224